Rivaroxaban Versus Warfarin and Risk of Post-Thrombotic Syndrome among Patients with Venous Thromboembolism

Background: The effectiveness of rivaroxaban to reduce post-thrombotic syndrome in patients with venous thromboembolism is largely unknown. We compared rates of post-thrombotic syndrome in patients given rivaroxaban versus warfarin in a cohort of patients with incident venous thromboembolism receiving routine clinical care. Methods: We linked Danish nationwide registries to identify all patients with incident venous thromboembolism who were new users of rivaroxaban or warfarin and compared rates of post-thrombotic syndrome using an inverse probability of treatment-weighting approach to account for baseline confounding. Results: We identified 19,957 oral anticoagulation–naive patients with incident venous thromboembolism treated with warfarin or rivaroxaban (mean age, 64 years; 48% were female, 45.5% had pulmonary embolism). The propensity-weighted rate of post-thrombotic syndrome at 3 years follow-up was 0.53 incidents per 100 person-years with rivaroxaban versus 0.55 per 100 person-years with warfarin, yielding a hazard rate of 0.88 (95% confidence interval, 0.66-1.17). This association remained consistent across types of venous thromboembolism (deep venous thrombosis vs pulmonary embolism, and provoked vs unprovoked venous thromboembolism) and when censoring patients with recurrent venous thromboembolism. Conclusions: In this clinical practice setting, rivaroxaban was associated with lower but statistically nonsignificant rates of post-thrombotic syndrome, which did not appear to be mediated only by an effect on recurrent venous thromboembolism.